1. Field of the Invention
This invention relates in general to purification of gases and in particular to an advantageous method for the removal of phosphine and arsine from silane as well as the quantitative analysis of phosphine and arsine in silane.
2. Description of the Prior Art
Silane gas is pyrophoric and those skilled in the art recognize that it reacts with many substances. The semiconductor industry uses large amounts of silicon which are produced from gases including silane. Sinoe phosphine (PH.sub.3) and arsine (AsH.sub.3) are common contaminants in silane and are also known to affect the electrical properties of semiconductor silicon, gases used for the prep ration of such silicon must necessarily be low in content of these impurities to reduce contamination of the silicon product.
Thus there exists a need for a process to remove arsine and phosphine from silicon while guarding against reaction of the silane gas containing the impurities.
The semiconductor industry often requires a silicon starting material having as little as a few parts per billion or a few tenths of one part per billion of phosphorus or arsenic. This often may only be achieved by starting with a silane gas precursor which contains equally small quantities of contaminants. Since such tiny portions of contaminants are critical, it has been extremely difficult to devise such precise analytical techniques as will determine the amount of phosphine and arsine in a sample of silane gas.